You spend a lot of time thinking about Facebook or plan use of Facebook.

You feel an urge to use Facebook more and more.

You use Facebook in order to forget about personal problems.

You have tried to cut down on the use of Facebook without success.

You become restless or troubled if you are prohibited from using Facebook.

You use Facebook so much that it has had a negative impact on your job/studies.

People are asked to self-report how each statement applies to them: (1) very rarely, (2) rarely, (3) sometimes, (4) often, and (5) very often.

The researchers found that people who indicate "often" or "very often" on four or more of the statements may be experiencing a Facebook addiction--and women are at greatest risk, according to the study. People with poor sleep habits also score high on the scale.

"It occurs more regularly among younger than older users," study author Dr. Cecilie Schou Andreassen, a psychologist at the university, said in a written statement. "We have also found that people who are anxious and socially insecure use Facebook more than those with lower scores on those traits, probably because those who are anxious find it easier to communicate via social media than face-to-face."

Plus, let's face it, avoiding Facebook is tough. Recent research from the University of Chicago suggests that social media are more addictive than sex.

About two-thirds of adults online--66 percent--say they use some type of social media like Facebook or Twitter, according to the Pew Research Center.